The present disclosure relates generally to communication systems, and more particularly, to downlink operations with shortened transmission time intervals (TTIs) for managing communications of one or more user equipment (UE) in a wireless communications system.
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources. Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). LTE is designed to support mobile broadband access through improved spectral efficiency, lowered costs, and improved services using OFDMA on the downlink, SC-FDMA on the uplink, and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. These improvements may also be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
In wireless communications systems employing legacy LTE, a plurality of UEs served by a particular eNodeB may receive data from the eNodeB over a shared downlink channel called the Physical Downlink Shared Channel (PDSCH). In addition, control information associated with the PDSCH may be transmitted to the UEs by the eNodeB via a Physical Downlink Control Channel (PDCCH) and/or an Enhanced PDCCH (ePDCCH). The control information included in the PDCCH or ePDCCH may include one or more uplink or downlink resource element (RE) grants for an LTE subframe. In legacy LTE, each LTE subframe has a transmission time interval (TTI) of 1 ms and is divided into two 0.5 ms slots. For example, UE specific reference signals (RSs) may be inserted into a transmission signal structure once synchronization between a UE and the eNodeB is complete. A UE specific RS may only be embedded in resource blocks (RBs) for which the PDSCH is mapped, and if transmitted, the UE is expected to use the RS to derive a channel estimate for demodulating data in the PDSCH RBs. The RS may provide a reference point for downlink power and may enable beamforming for transmissions between the UE and eNodeB. However, due to increasing complexities for resource scheduling, increased flexibility of RS management is desired for demodulation of a downlink communication channel.
As such, improvements in utilization of reference signals for managing communications of one or more UE in a wireless communications system are needed.